This invention relates to a V-type internal combustion engine, and more particularly to a V-engine for use in a marine propulsion system.
In a marine propulsion system including an engine, a transmission, and a propeller, it has been found that providing an increase in engine torque in a certain range of engine rpm at rated horsepower significantly enhances boat performance due to the capacity of the propeller to absorb engine torque under extreme conditions. One method for providing additional torque to the propeller in the relevant range of engine rpm at rated horsepower to enhance boat performance has involved use of a torque converter in conjunction with the transmission between the engine and the propeller. However, adding a torque converter can increase the complexity and cost of the transmission, and may not be an entirely satisfactory means for providing such increased torque.
The present invention provides a means for increasing the torque produced by a V-type engine without adding a torque converter or otherwise modifying the marine transmission. In accordance with the invention, a V-engine for marine application comprises a pair of cylinder banks having a plurality of cylinders, with the banks being oppositely slanted with respect to each other to form a V-shaped engine configuration. The upper ends of each cylinder in the pair of cylinder banks have an intake port for receiving an air-fuel mixture and an exhaust port for exhausting spent gases from the cylinders. The intake ports of each cylinder receive the air-fuel mixture from a supply means furnishing the mixture from outside the valley of the V-shaped configuration, and the exhaust ports exhaust the spent gases toward the valley of the V-shaped configuration. In accordance with one embodiment of the invention, an exhaust collection means, such as an exhaust manifold, is disposed in the valley of the V-shaped engine adjacent the engine block for collecting exhaust gases exhausted from the cylinders through the exhaust ports. The supply means comprises induction means for introducing the air-fuel mixture to the intake ports from outside the valley of the V-shaped engine and, in a preferred embodiment, the induction means comprises a plurality of induction tubes supplying the air-fuel mixture to the intake ports. The induction tubes are connected at one end to the V-shaped engine for passing the air-fuel mixture to the intake ports, and are connected at their other end to an intake manifold. In the preferred embodiment, the intake manifold is disposed in the valley of the V-shaped engine, and is located adjacent the exhaust manifold. Heat from the exhaust gases contained in the exhaust manifold or the engine cooling water is used to pre-heat air supplied to the intake ports via the induction tubes to provide efficient low-speed operation of the boat. A single exhaust outlet is provided from the exhaust manifold to discharge exhaust gases from the manifold through the exhaust system.
With the above construction, the induction tubes passing the air-fuel mixture to the cylinders are designed to provide "ram" type induction to the cylinders. As is known, this type of induction increases the amount of air-fuel mixture passing to the cylinders and available for the combustion cycle. With proper design of the induction tubes, an increase in engine torque by such increase in the amount of air-fuel mixture available for combustion is provided in the appropriate range of engine rpm at rated horsepower to enhance boat performance.
A further advantage offered by this construction of the V-type engine is that separate exhaust manifolds, generally located on the sides of the engine, are eliminated. In the past, V-type engines used in marine propulsion applications have closely resembled engines used in automotive applications, wherein an intake manifold is provided in the valley of the V-shaped engine with exhaust manifolds on either side of the engine connected to the cylinder heads. However, in marine applications, the exhaust manifolds are usually water-jacketed so as to provide cooling of the exhaust prior to discharge through the exhaust system. Such water-jacketed manifolds are heavy and bulky and, suspended from the sides of the engine, create substantial stresses on the engine block. This form of V-type engine construction also increases the overall width of the engine package. By eliminating the side-mounted exhaust manifolds, the present invention provides an engine package significantly narrower than previous engines, and in which the overall efficiency of engine component placement is increased. A single, well supported exhaust manifold discharges exhaust through a single outlet, thus providing an advantageous exhaust system.